Computer Programming

1. Computer Programming

2. Why are People Afraid of Programming? • Don’t want to be a “nerd” • Computer languages are hard • What if I don’t understand? • Why should I? Everything has already been invented.

3. Why Should I Learn to Program? • Some people find it fun. • It is a satisfying means to an end – learn to use a wonderful tool • Learn a new way to think and improve general problem solving skills

4. Computer Programming • What is computer programming? • Process of writing, testing, debugging, and maintaining the source code of computer programs. • What is a computer program? • A set of instructions that tells the computer what to do. There are many ways to give these instructions – how you do it matters. Learning to program helps shape your thoughts .

5. Computer Programming • Where does code come from? • Written in a programming language from scratch • Modified from existing code

6. Computer Programming • Why do we do it? • To create a program that performs a desired behavior. • There is some debate as to whether programming is an art, a craft, or an engineering discipline.

7. Computer Programming • Programmers work to create code that is efficient (works without draining current resources) and evolvable (can become something bigger in the future) • Programmers hope their code is considered “elegant” (i.e. well written) • Programmers are generally given a list of requirements and then work to translate those requirements into something the computer can understand.

8. Computer Programming • Programming is often compared to following a recipe. • Programming is about giving the computer step by step instructions to go about completing the task. • The instructions generally take the form of: • a direct statement • a conditional statement • a link to a group of statements • a loop around statements meant to be repeated for some amount of time.

9. Computer Programming • Programming typically tries to break up large tasks into smaller, more manageable ones. • Often, the program is required to compute a result. • Programmers describe their code to others from within using documentation.

10. Pizza Dough Recipe (Requirements)‏ 1. Gather Ingredients 2. Combine sugar (1tbs), salt (1tbs), olive oil (1tbs), flour (1c) in mixing bowl 3. Turn on mixer 4. Add 1/4 cup of flour 5. If dough comes off the sides go to step 6, otherwise go back to step 4 6. Knead 15 minutes 7. Let rest for at least 45 minutes in warm area • 1 dough ball

11. N-Pizza Dough Program • Gather Ingredients • Combine sugar (N tbs), salt (N tbs), olive oil (N tbs), flour (N c) in mixing bowl • Turn on mixer • Add N/4 cup of flour • If dough comes off the sides go to step 6, otherwise go back to step 4 • Knead 15 minutes • Let rest for at least 45 minutes in warm area • N dough balls

12. N-Pizza Dough Program • Gather Ingredients • Combine sugar (N tbs), salt (N tbs), olive oil (N tbs), flour (N c) in mixing bowl • Turn on mixer • Add N/4 cup of flour • If dough comes off the sides go to step 6, otherwise go back to step 4 • Knead 15 minutes • Let rest for at least 45 minutes in warm area Sequence of Statements • N dough balls

13. N-Pizza Dough Program • Gather Ingredients • Combine sugar (N tbs), salt (N tbs), olive oil (N tbs), flour (N c) in mixing bowl • Turn on mixer • Add N/4 cup of flour • If dough comes off the sides go to step 6, otherwise go back to step 4 • Knead 15 minutes • Let rest for at least 45 minutes in warm area Variable • N dough balls

14. N-Pizza Dough - Program • Gather Ingredients • Combine sugar (N tbs), salt (N tbs), olive oil (N tbs), flour (N c) in mixing bowl • Turn on mixer • Add N/4 cup of flour • If dough comes off the sides go to step 6, otherwise go back to step 4 • Knead 15 minutes • Let rest for at least 45 minutes in warm area Conditional

15. N-Pizza Dough - Program • Gather Ingredients • Combine sugar (N tbs), salt (N tbs), olive oil (N tbs), flour (N c) in mixing bowl • Turn on mixer • Add N/4 cup of flour • If dough comes off the sides go to step 6, otherwise go back to step 4 • Knead 15 minutes • Let rest for at least 45 minutes in warm area Subroutines Mini-programs • N dough balls

16. Programming Languages • There are hundreds of different programming languages. • A few basic types of instructions appear in all of them • Input (get input from the user) • Output (display data to the user on a monitor or printout) • Math (perform basic mathematical operations) • Conditional Execution (check for conditions and execute the appropriate sequence of statements) • Repetition (perform some sequences of statements repeatedly)

17. What is Programming? • Using the tools of the language and the ideas discussed above is really what computer programming is all about • Computers only “understand” about 100 different types of instructions. However, there are millions of permutations of these. • Think Chess – 6 pieces that move in simple patterns – why is it a complicated game?

18. Programming Benefits • Learning how to arrange a sequence of instructions to carry out a task is the most valuable thing you really learn. That involves understanding: • Mathematical and computational ideas • Coordinates, Variables, Random Numbers • Problem solving skills • Process of Design • Idea->Prototype->Experiments->Debugging->Redesign->New Ideas • Fluency with Digital Technology • To be fluent in language, you learn to read AND write – how to express yourself in the language. The same is true of programming – using the computer not just to interact but to create.

19. Programming Languages • There are hundreds of programming languages and several categories where the languages fall • A few types include • Imperative • Structured • Procedural • Declarative • Functional • Logical • Object-Oriented • Event Driven • Scripting • Markup • Graphical

20. Imperative Programming Languages • A programming paradigm (i.e. style of programming) that describes computation in terms of statements that change a program state. • In natural languages, the imperative mood expresses commands to take action. • Similarly, imperative programs define sequences of commands for the computer to perform.

21. Structured Programming • Programming paradigm aimed on improving the clarity, quality, and development time of a computer program • Uses subroutines, block structures, and for or while loops • Idea emerged in the 1960’s. • ALGOL was an early example.

22. Procedural Programming • Type of Imperative Programming derived from Structured Programming based on concept of procedure call • Programs contain a list of instructions telling the computer what to do, step-by-step, usually having a linear order of execution from the first statement to the second to the last, with occasional loops and branches to subprograms. • Procedures (aka: routines, subroutines, methods, functions) are subprograms that contain step by step instructions for the program to carry out. Can be called at any time during a program’s execution. • EXAMPLES: BASIC, Pascal, C

23. Declarative Programming • Programming paradigm that expresses the logic of a computation without describing the control flow. • Describe what the program should accomplish instead of how to accomplish it. • Directly in contrast with imperative programming (describing algorithms in explicit steps) • Considers programs as theories of formal logic and computations as deductions in that logic space. • Examples include database query languages (SQL), regular expressions, logic programming, and functional programming

24. Functional Programming • Programming paradigm that treats computation as the evaluation of mathematical functions. • Roots in lambda calculus. • Attempt to remove the “side effects” that can occur in imperative programming • Output value of the functions depends only on the arguments that are input to the function. Therefore, calling a function with the same inputs will always produce the same results. • Makes behavior of program more predictable • Examples include Common Lisp, Scheme, and is supported in Mathematica • Programming in a functional style can take place in imperative programming languages

25. Logical Programming • Programming paradigm consists of a set of axioms (facts/rules) and a goal statement. • Rules of inference are applied to determine if axioms are sufficient to ensure truth of goal statement • Execution corresponds to construction of a proof of the goal statement from the axioms • Programmer specifies basic logical relationships and does not specify the way the inference rules are applied • Prolog is considered a logical programming language. An example of prolog code is here: http://williams.comp.ncat.edu/COMP360/Prologfamily.htm

26. Application Areas of Logical Programming • Relational Data Bases • Natural Language Interfaces • Expert Systems • Symbolic Equation solving • Planning • Prototyping • Simulation • Programming Language Implementation

27. Object Oriented Programming • Programming paradigm that represents concepts as “objects” • Objects have data fields – attributes that describe the object are called “methods” – methods perform the actions of the object and can modify the data fields • Objects are instances of classes and interact with each other to design applications. • Examples: Smalltalk, C++, Java

28. Event Driven Programming • Programming paradigm where the flow of the program is determined by events • Events include mouse clicks, key presses, and messages from other programs (aka threads) • Can be written in any language, but easier in some than others.

29. Scripting Language • Programming language that support writing scripts • Scripts work to automate the execution of tasks that normally take a human operator several one-by-one steps. • Can be used in software applications, web pages within a browser, shells of operating systems, and used in embedded systems. • Small programs (sometimes just a few lines, never more than a few thousand lines)

30. Markup Languages • A language that “marks up” text, usually for some means of display • Used in most word processors to indicate locations of paragraphs, font type, etc. (TeX, LaTeX) • Structural markers can also be used (XML) • Some have pre-defined presentation semantics (HTML, XHTML)

31. Graphical Programming Languages • Any programming language that lets users create programs by manipulating program elements graphically rather than by specifying them textually. • Examples include Alice, Scratch, App Inventor

32. Programming • Many see programming as a tedious, specialized activity • Traditional programming languages can be difficult to learn at first. • Recent developments have worked to create graphical programming languages • Makes programming more engaging and accessible to those first learning